Double-tube type heat exchanger and refrigerating machine using the heat

ABSTRACT

A double-tube type heat exchanger has a restriction hole ( 6 ), formed on an inner tube ( 3 ), through which a refrigerant introduced into an outer tube ( 3 ) is introduced into the inner tube ( 3 ) while the refrigerant expands. Therefore, a part of the refrigerant introduced into the outer tube ( 3 ) can be introduced into the inner tube ( 2 ) from the restriction hole ( 6 ) while the refrigerant expands. That is, the restriction hole ( 6 ) formed on the inner tube ( 2 ) serves as an expansion mechanism of a bypass flow. Therefore, this double-tube type heat exchanger ( 1 ) allows an injection circuit or a super-cooling circuit to be compactly and inexpensively constructed.

This application is the national phase under 35 U.S.C. §371 of PCTInternational Application No. PCT/JP99/03931 which has an Internationalfiling date of Jul. 22, 1999, which designated the United States ofAmerica.

TECHNICAL FIELD

The present invention relates to a double-tube type heat exchanger to beused for a super-cooling circuit of a refrigerator and a gas injectioncircuit thereof to perform heat-exchange between a main flow of arefrigerant and a bypass flow thereof and a refrigerator using it.

BACKGROUND ART

As shown in FIG. 2, a double-tube type heat exchanger having acylindrical inner tube 101 and an outer tube 102 so surrounding theperipheral surface of the inner tube 101 as to enclose it is known. Aport 105 at one end of the outer tube 102 of a double-tube type heatexchanger 103 is connected to an outflow end 107A of a rectificationcircuit 107, while a port 106 at the other end of the outer tube 102 isconnected to an inflow end 107B of the rectification circuit 107 via amain electromotive-expansion valve 108. The outflow end 107A isconnected to an hole 111 of the inner tube 101 on the upstream sidethereof via a bypass electromotive-expansion valve 112. An hole 113 ofthe inner tube 101 on the downstream side thereof is connected to abypass pipe 115.

The rectification circuit 107 has four check valves 121, 122, 123, and124 connected in a forward direction from the inflow end 107B to theoutflow end 107A. A connection pipe 107C connecting the check valves 121and 123 to each other and a connection pipe 107D connecting the checkvalves 122 and 124 to each other serve as the connection pipes connectedto a main-flow circuit. A thermostat 119 installed on a bypass pipe 114detects the temperature of a bypass-flow refrigerant. Temperatureinformation detected by the thermostat 119 is used to control an opendegree of the bypass electromotive-expansion valve 112.

As shown in FIG. 3, a gas injection circuit can be constructed byconnecting the bypass pipe 115 to an intermediate-pressure position of acompressor 116 and by connecting connection pipes 107C and 107D to anoutdoor heat exchanger 201 and an indoor heat exchanger 202,respectively. According to the gas injection circuit, in a cooling time,a refrigerant discharged from the outdoor heat exchanger 201 serving asa condenser is expanded by the bypass electromotive-expansion valve 112and introduced into the inner tube 101. After the refrigerant is heatedby a main-flow refrigerant inside the outer tube 102, it can be injectedto the intermediate-pressure position of the compressor 116 via thebypass pipe 115. In a heating time, a refrigerant discharged from theindoor heat exchanger 202 serving as a condenser is heated by arefrigerant inside the outer tube 102 after the refrigerant passesthrough the bypass electromotive-expansion valve 112 and the inner tube101. Then, the refrigerant can be injected to the intermediate-pressureposition of the compressor 116 via the bypass pipe 115.

As shown in FIG. 4, by connecting the bypass pipe 115 to an intake sideof the compressor 116 and connecting the connection pipes 107C and 107Dto the outdoor heat exchanger 201 and the indoor heat exchanger 202,respectively, a super-cooling circuit can be constructed. According tothe super-cooling circuit, in a cooling time, a refrigerant dischargedfrom the outdoor heat exchanger 201 is expanded by the bypass expansionvalve 112 and introduced into the inner tube 101. After a main-flowrefrigerant inside the outer tube 102 is super-cooled, the refrigerantcan be returned to the intake side of the compressor 116 via the bypasspipe 115. In a heating time, a refrigerant discharged from the indoorheat exchanger 202 is expanded by the bypass electromotive-expansionvalve 112 and introduced into the inner tube 101. After the main-flowrefrigerant inside the outer tube 102 is super-cooled, the refrigerantcan be returned to the intake side of the compressor 116 via the bypasspipe 115.

However, according to the conventional double-tube type heat exchanger103, in order to construct the gas injection circuit or thesuper-cooling circuit, a pressure-reducing mechanism, namely, the bypasselectromotive-expansion valve 112 is required as described above. Thebypass electromotive-expansion valve 112 causes the construction of theconventional double-tube type heat exchanger 103 to be complicated andits cost to increase.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide adouble-tube type heat exchanger allowing a gas injection circuit or asuper-cooling circuit to be compact and inexpensive and provide arefrigerator using the above double-tube type heat exchanger.

To achieve the object, the present invention provides a double-tube typeheat exchanger for heat-exchanging between a refrigerant flowing throughan outer passage and a refrigerant flowing through an inner passage,comprising a restriction passage, communicating between the innerpassage and the outer passage, through which a refrigerant introducedinto the outer passage is introduced into the inner passage while therefrigerant of the outer passage expands.

In the double-tube type heat exchanger of the present invention, a partof the refrigerant introduced into the outer passage is introduced intothe inner passage through the restriction passage while the refrigerantof the outer passage expands. Heat exchange is made between the expandedbypass refrigerant introduced into the inner passage and the main-flowrefrigerant flowing in the outer passage. Accordingly, in the case wherea gas injection circuit is constructed from the double-tube type heatexchanger of the present invention, the bypass refrigerant can begasified with the main-flow refrigerant. In the case where asuper-cooling circuit is constructed from the double-tube type heatexchanger of the present invention, the main-flow refrigerant can besuper-cooled with the bypass refrigerant.

According to the double-tube type heat exchanger of the presentinvention, the restriction passage allowing communication between theinner passage and the outer passage with each other serves as anexpansion mechanism for a bypass flow. Therefore, it is possible toconstruct the injection circuit and the super-cooling circuit which arecompact and inexpensive.

In one embodiment of the present invention, there is provided arefrigerator comprising a gas injection circuit having the double-tubetype heat exchanger wherein an inflow port of an outer passage of thedouble-tube type heat exchanger is connected to a condenser, an outflowport of the outer passage is connected to an evaporator via an expansionmechanism, and an outflow port of the inner passage is connected to anintermediate-pressure position of a compressor with a bypass pipe.

According to the refrigerator of this embodiment, the restrictionpassage of the double-tube type heat exchanger serves as an expansionmechanism for the gas injection circuit. Therefore, it is possible toconstruct the refrigerator having the compact and inexpensive gasinjection circuit without adding a pressure-reducing mechanism thereto.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of a circuit including a double-tube type heatexchanger of an embodiment of the present invention and a rectificationcircuit;

FIG. 2 is a diagram of a circuit having a conventional double-tube typeheat exchanger;

FIG. 3 is a circuit diagram of a refrigerator including a gas injectioncircuit having the conventional double-tube type heat exchanger; and

FIG. 4 is a circuit diagram of a refrigerator including a super-coolingcircuit having the conventional double-tube type heat exchanger;

FIG. 5 is a circuit diagram of a refrigerator including a gas injectioncircuit having the double-tube type heat exchanger of the presentinvention; and

FIG. 6 is a circuit diagram of a refrigerator including a super-cooledcircuit having the double-tube type heat exchanger of the presentinvention.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention will be described in detail below with referenceto embodiments shown in the drawings.

FIG. 1 shows an embodiment of a double-tube type heat exchanger of thepresent invention. The double-tube type heat exchanger 1 has an innertube 2 and an outer tube 3. The inner tube 2 is approximatelycylindrical. One end 2A of the inner tube 2 is closed, whereas the otherend 2B thereof is open to form a port 5. A small-diameter restrictionhole 6 serving as a restriction passage is formed on a peripheralsurface of the inner tube 2 such that the restriction hole 6 is locatedin the vicinity of the one end 2A of the inner tube 2. The outer tube 3is so fixed to the peripheral surface of the inner tube 2 as to enclosea part 2C of the inner tube 2 between both the ends 2A and 2B thereof.The outer tube 3 has an inlet 7 and an outlet 8 in the neighborhood ofone and other ends of a peripheral surface 3A thereof, respectively.

The inlet 7 of the outer tube 3 of the double-tube type heat exchanger 1is connected to an outflow end 15A of a rectification circuit 15constructed of four check values 11, 12, 13, and 14. The outlet 8 of theouter tube 3 is connected to an inflow end 15B of the rectificationcircuit 15 via a main electromotive-expansion valve 16. The port 5 ofthe inner tube 2 of the double-tube type heat exchanger 1 is connectedto a bypass pipe 20 having an electromagnetic valve 18 installedthereon.

The check valves 11, 12, 13, and 14 constituting the rectificationcircuit 15 are connected in a forward direction from the inflow end 15Bto the outflow end 15A such that the check valves 11 and 13 areconnected in series with each other and the check valves 12 and 14 areconnected in series with each other. A connection point 15C of the checkvalves 11 and 13 and a connection point 15D of the check valves 12 and14 are connected to a main-flow refrigerant circuit. That is, a circuit25 constructed of the double-tube type heat exchanger 1 and therectification circuit 15 shown in FIG. 1 constitutes a gas injectioncircuit or a super-cooling circuit by replacing, with the circuit 25,the circuit 130 which includes the conventional double-tube type heatexchanger 103 and is surrounded with a broken line as shown in FIGS. 3and 4.

Description on an operation of a refrigerator is made below in the casewhere the gas injection circuit is formed by replacing the conventionalcircuit 130 shown in FIG. 3 with the circuit 25 having the above-stateddouble-tube type heat exchanger 1. In this case, in a cooling time whena four-way selector valve 203 is switched to select paths shown withsolid lines, a refrigerant discharged from the outdoor heat exchange 201serving as a condenser is introduced into the inlet 7 of the outer tube3 of the double-tube type heat exchanger 1 through the check valve 11 ofthe rectification circuit 15. A refrigerant serving as a main flow ofthe refrigerant introduced into the inlet 7 of the outer tube 3 isdischarged from the outlet 8 through the outer tube 3, is expanded bythe main electromotive-expansion valve 16, passes through the checkvalve 14 of the rectification circuit 15, and is introduced into theindoor heat exchanger 202 operating as an evaporator. On the other hand,of the refrigerant introduced into the inlet 7 of the outer tube 3, arefrigerant which has entered the inner tube 2 from the small-diameterrestriction hole 6 while the refrigerant expands is heat-exchanged withthe main-flow refrigerant, is gasified, is discharged from the port 5 ofthe other end 2B, passes through the electromagnetic valve 18 of thebypass pipe 20, and is injected to the intermediate-pressure position ofthe compressor 116. In a heating time when the four-way selector valve203 is switched to select paths shown with broken lines, a refrigerantdischarged from the indoor heat exchange 202 serving as a condenser isintroduced into the inlet 7 of the outer tube 3 of the double-tube typeheat exchanger 1 through the check valve 12 of the rectification circuit15. A refrigerant serving as a main flow of the refrigerant introducedinto the inlet 7 of the outer tube 3 is discharged from the outlet 8through the outer tube 3, is expanded by the mainelectromotive-expansion valve 16, passes through the check valve 13 ofthe rectification circuit 15, and is introduced into the outdoor heatexchanger 201 operating as an evaporator. On the other hand, of therefrigerant introduced into the inlet 7 of the outer tube 3, arefrigerant which has entered the inner tube 2 from the small-diameterrestriction hole 6 while the refrigerant expands is heat-exchanged withthe main-flow refrigerant, is gasified, is discharged from the port 5 ofthe other end 2B, passes through the electromagnetic valve 18 of thebypass pipe 20, and is injected to the intermediate-pressure position ofthe compressor 116. By hole and closing the electromagnetic valve 18,gas injection can be turned on and off.

As described above, according to the double-tube type heat exchanger 1of the embodiment, the small-diameter restriction hole 6 formed on theperipheral surface of the inner tube 2 serves as the bypasselectromotive-expansion valve 112 shown in FIGS. 3 and 4. Therefore, thedouble-tube type heat exchanger 1 allows a gas injection circuit to beconstructed without adding a pressure-reducing mechanism thereto. Thus,it is possible to prevent the gas injection circuit from beingcomplicated and its cost from being increased and allow it to be compactand inexpensive.

The circuit 25 shown in FIG. 1 can be used to construct a super-coolingcircuit by replacing the conventional circuit 130 shown in FIG. 4 withthe circuit 25. In this case, as in the case of the above-described gasinjection circuit, the small-diameter restriction hole. 6 formed on theinner tube 2 of the double-tube type heat exchanger 1 serves as anexpansion mechanism for a bypass flow. Therefore, it is possible toconstruct the super-cooling circuit without adding an expansionmechanism thereto. Therefore, it is possible to construct the compactand inexpensive super-cooling circuit.

In the above embodiment, the small-diameter restriction hole 6 formed onthe inner tube 2 serves as the restriction passage. However, asmall-diameter restriction tube connecting between the peripheralsurface 3A in the vicinity of the inlet 7 of the outer tube 3 and theend 2A of the inner tube 2 may be used as the restriction passage. Bythe restriction tube, the refrigerant introduced into the outer tube 3is introduced into the inner tube 2 while the refrigerant expands. Inthe description of the embodiment, the circuit 25 is constructed bycombining the double-tube type heat exchanger 1 and the rectificationcircuit 15 with each other to use it for cooling and heating purpose.When a refrigerator to which the double-tube type heat exchanger 1 isapplied is used for only cooling purpose, the rectification circuit 15may be omitted.

Industrial Applicability

The present invention is applicable to a double-tube type heat exchangerand a refrigerator using it and useful for constructing a compact andinexpensive gas injection circuit and super-cooling circuit.

What is claimed is:
 1. A double-tube type heat exchanger for the heatexchanging a refrigerant, comprising: an inner tube having a closed endand an open end; an outer tube having an inlet and an outlet, the outertube surrounding the inner tube; and a restriction passage formed on aperipheral surface of the inner tube and communicating between the innertube and the outer tube, wherein the refrigerant introduced into theouter tube is introduced into the inner tube while the refrigerant ofthe outer tube expands.
 2. The heat exchanger according to claim 1,wherein the restriction passage is located near the closed end of theinner tube.
 3. The heat exchanger according to claim 1, wherein the openend of the inner tube further comprises a port, the port connected to abypass pipe.
 4. The heat exchanger according to claim 3, wherein thebypass pipe further comprises an electromagnetic valve.
 5. The heatexchanger according to claim 1, wherein the inlet of the outer tube isconnected to an outflow end of a rectification circuit.
 6. The heatexchanger according to claim 5, wherein the outlet of the outer tube isconnected to an inflow end of the rectification circuit.
 7. The heatexchanger according to claim 6, wherein the inflow end of therectification circuit further comprises a main electromotive expansionvalve.
 8. The heat exchanger according to claim 5, wherein therectification circuit is constructed of four check valves.
 9. The heatexchanger according to claim 1, wherein the inlet of the outer tube isnear the closed end of the inner tube and the outlet of the outer tubeis near the open end of the inner tube.
 10. A gas injection circuithaving a double-tube type heat exchanger for heat exchanging arefrigerant including an inner tube having a closed end and an open end,an outer tube having an inlet and an outlet, and a restriction passagecommunicating between the inner tube and the outer tube, the gasinjection circuit comprising: a condenser connected to the inlet of theouter tube; an evaporator connected to the outlet of the outer tube,wherein an expansion mechanism is provided between the evaporator andthe outlet of the outer tube; and an outflow port in the inner tubeconnected to an intermediate-pressure position of a compressor with abypass pipe.
 11. A super cooling circuit having a double-tube type heatexchanger for heat exchanging a refrigerant including an inner tubehaving a closed end and an open end, an outer tube having an inlet andan outlet, and a restriction passage communicating between the innertube and the outer tube, the gas injection circuit comprising: acondenser connected to the inlet of the outer tube; an evaporatorconnected to the outlet of the outer tube, wherein an expansionmechanism is provided between the evaporator and the outlet of the outertube; and an outflow port in the inner tube connected to anintermediate-pressure position of a compressor with a bypass pipe.